U.S. Pat. No. 4,958,430 describes a method for manufacturing an orifice disk for a fuel injector from a flat metal strip that is processed by passing the strip through a progressive die. The finished orifice disk is a circle that comprises a central circular orifice. After the orifice disk has been assembled into the nozzle end of a fuel injector, the central circular orifice serves to meter the flow of fuel from the fuel injector. The circular orifice is created by punching a hole in the metal and then coining it.
Because the orifice performs a metering function, its dimensions are important in securing metering accuracy. It is fair to say that the greater the precision in those dimensions, the greater the metering accuracy.
The present invention arises in consequence of seeking further improvements in metering accuracy of an orifice disk member of a fuel injector. Briefly, the invention comprises an orifice disk that is fabricated from a strip of clad metal wherein the clad metal comprises a soft metal lamina overlay on a refractory metal lamina. An orifice is created by first punching a hole in the clad metal and then selectively etching the soft metal lamina around the punched hole. The selective etching is conducted in a manner that creates a taper in the direction of flow through the orifice. In this way the orifice is provided with a tapered entrance portion leading to a circular exit portion.
A preliminary novelty search conducted in connection with this invention developed U.S. Pat. Nos. 3,653,997 and 719,536.
The invention will be explained in detail in the ensuing description which is accompanied by a drawing illustrating a presently preferred embodiment according to the best mode contemplated at this time for carrying out the invention.